Immersion heater element

ABSTRACT

An immersion heater comprising essentially a coil obtained by winding coilwise cable sections adapted to heat in their central portions and remain cold at their ends, and a tube containing the cold outlets of said coil and of a connector for securing the immersion heater to the edge of the vessel containing the fluid to be heated is characterized in that the turns of the coil are supported by flexible and resistant longitudinal rodlike elements assembled on the same side of the coil as the cold ends thereof, and sealed in the outlet tube. This immersion heater further comprises an electrical relay following the fastening connector. The coil and tube assembly is housed in an insulating sheath formed with slots.

[ 51 July 4, 1972 [54] IMMERSION HEATER ELEMENT [72] Inventor: BeatriceRagault, 27 Bois Jerome par Vernon, France [22] Filed: Jan. 14, 1971 21Appl.No.: 106,484

[30] Foreign Application Priority Data Jan. 16, 1970 France ..7001495[52] U.S.Cl ..219/523,2l9/336,219/536, 219/550, 219/552, 338/296 [51]Int. Cl. ..H05b 3/06 [58] Field ofSearch ..219/523, 335-336, 219/381,536, 541-542, 548, 550, 552-553;

[56] References Cited UNITED STATES PATENTS 3,371,192 2/1968 Rosenal..219/523 5 5 (AIIIAIAIAIIAIA 3,218,437 11/1965 Laing ..219/536 X3,458,766 7/1969 Little ..317/98 3,476,915 l1/1969 Rapsis ..219/5233,617,701 11/1971 Volker ..219/336 Primary ExaminerVolodymyr Y. MayewskyAttorney-Robert E. Burns and Emmanuel J. Lobato [5 7] ABSTRACT Animmersion heater comprising essentially a coil obtained by windingcoilwise cable sections adapted to heat in their central portions andremain cold at their ends, and a tube containing the cold outlets ofsaid coil and of a connector for securing the immersion heater to theedge of the vessel containing the fluid to be heated is characterized inthat the turns of the coil are supported by flexible and resistantlongitudinal rodlike elements assembled on the same side of the coil asthe cold ends thereof, and sealed in the outlet tube. This immersionheater further comprises an electrical relay following the fasteningconnector. The coil and tube assembly is housed in an insulating sheathformed with slots.

4 Claims, 5 Drawing Figures 1 IMMERSION HEATER ELEMENT SUMMARY OF THEINVENTION The present invention relates to immersion heaters or heatingplungers of the type utilinng insulated heating cables or conductorsadapted to emit heat by Joule effect under welldefmed conditions ofoperation, so as to avoid any damage to the insulating material, thesedevices comprising cold conductors, i.e. outlets of which only thecentral section is heated appreciably, the ends being scarcely heated orremaining cold along a more or less extended portion.

An immersion heater according to this invention comprises essentially acold-outlet heating cable wound coilwise to constitute a coil of whichthe turns are interconnected by longitudinal rods, by using an adequatefastening or tying wire. Said rods may consist of the side branches ofhairpin-like members of which at least one acts as a non-heating returnend element of the heating cable. These rods and cable returns areconnected to the same or common end of the coil.

A device for mechanically assembling these non-heating ends of the cableand the rods associated therewith comprises a tube provided at its inletend with a plug of elastomeric material, through which said ends arecaused to extend, said tube being filled for sealing purposes with asuitable holding compound or material.

A hollow elbow connects this tube to a device for securing the immersionheater or plunger to the edge of the vessel containing the liquid to beheated and also for protecting the cold outlets of the heating cable.

This elbow is connected in turn to an insulating tube receiving thecable outlets or a fluid-tight electrical relay device which permitsconnecting in a tight manner a multiple-conductor cable having a plasticor rubber insulation of any suitable commercial type. The sealing efiectinvolving the electrical insulation under any weather conditions isobtained by using suitable perforated elastomer plugs at the end of thistube.

A plastic tube protection sheath device formed with suitableperforations is centered with respect to the coil by said rods so as topreclude any direct contact between said protection sheath device andsaid coil.

BRIEF DESCRIPTION OF THE DRAWING A preferred form of embodiment of theimmersion heater according to this invention will now be described withreference to the accompanying drawing, in which:

FIG. I is a diagrammatic elevational view with parts broken away showingthe heating section and the non-heating section of the device, with theconnecting means thereof;

FIG. 2 is an elevational fragmentary view showing one portion of theheating section of the device during the assembling operation;

FIG. 3 is a corresponding end view;

FIG. 4 is a fragmentary axial section showing a relay for connecting thedevice to the supply cable;

FIG. 5 is a fragmentary elevational view, with parts broken away,showing the immersion heater of this invention without the relay of FIG.4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The immersion heater accordingto this invention comprises essentially a cable I wound to form helicalturns on a cylindrical mandrel 3 comprising a number of longitudinalgrooves 4 disposed at spaced intervals on its outer surface, theexemplary form of embodiment illustrated comprising three grooves 4spaced 120 from one another. Preferably, the cable is of the heatingtype with cold outlets, all the heating section and a small non-heatingsection of this cable being wound to constitute a heating coil 7. Then,a longitudinal rod 5 of different material but capable of resistingchemical agents, such as a steel wire coated with a plastic film byextrusion or threading, is so disposed as to register with each groove 4and secured in position by temporary means. Then, by operating accordingto the methods of commercial basketwork technique, facilitated by thepresence of said grooves 4, the rods 5 may be secured to the cable 1 ateach intersection obtained therebetween, for example by using a wire 6consisting either of a monofilament of suitable plastic material, i.e.heat-resistant and insensitive to chemical agents, or a wire sheathedwith suitable plastic material, or any other material such as glassfiber yarn, with or without protection coating or the like.

According to an application of current commercial type the followingdimensions have been used: diameter of mandrel 3 28 mm; diameter ofcable 1 3.8 mm; diameter of rods 5 3 mm; diameter of wire 6 1 mm, andlength of cold outlet 10 cm.

The order of magnitude of the cable diameter, for example within therange of 2.5 to 5 mm, is essential for the purpose of the presentinvention, for:

if a smaller diameter were used, the step of bending the cable 1 on rods5 would lead to prohibitive cost and complication;

if a larger diameter were used, the cable 1 would not accommodate radiiof curvature permitting the production of immersion heaters havingsuitable over-all dimensions;

if different diameters were used, the temperature gradient from the coreto the outer periphery would be changed and become remote from the idealproportion existing between the primary insulation of the cable: 260 C,and the secondary insulation 205 C.

If the rod 5 consists of a plastic-coated wire, it is preferable to keepthe ends of this wire outside the fluid to be heated in order to avoidthe attack of the branches by chemicals. The rods 5 may advantageouslyconsist of an even number of rectilinear sections interconnected attheir ends by continuous curves, i.e. hairpins 18, without anydiscontinuity in their protection.

At a same end of the coil thus obtained the two ends 26, 28 of theheating cable and the ends 25, 27 of rods are assembled, the third rod 5consisting of a non-heating return of the heating cable. Thus, the twoends 26, 28 of cable 1 and the two ends 25, 27 of the hairpin areassembled at one end of said coil.

The advantages deriving from this arrangement may be summarized asfollows: firstly, it ensures a strict control of the relative spacing ofthe various cable sections, without allowing these sections to contactone another, while maintaining them sufficiently close to each other tospare space. It also avoids unduly large contact areas with the cablesupports that are not heat conductive, as would be the case if the cablewere wound directly for example on a tube of plastic material; in fact,in this case abnormal heating would take place and prove detrimental tothe useful life of the cable insulation at these points of contact, andthus interfere with the circulation or renewal of the liquid around thecable. In all cases, these points of contact must be reduced to aminimum.

Another advantage deriving from this device is that all the cablesurface is perfectly and easily accessible, this feature beingparticularly valuable for cleaning purposes; in fact, thischaracteristic although quite obvious as far as the outer surface of thecoil is concerned, is also useful for the inside, which, after themounting mandrel 3 has been removed by slipping, appears as a hollowcylindrical body of circular crosssection which, owing to its particulardimensions, is easily accessible for cleaning purpose by using acircular brush of suitable dimensions.

These features are of primary importance for it is known in the art thatthe heating elements immersed in certain fluids, such as those of brightnickel, for instance, become regularly coated with a muddy deposit whichmust compulsorily be removed at suitable time intervals. On the otherhand in this respect it may be pointed out that if the heating cable hasbeen properly made these deposits, given an equal heating power, arereduced considerably in comparison with conventional heating devices ofthe immersion type, notably in that they do not adhere to the cable.However, the cable must be so arranged that an inspection and a lightcleaning operation by means of soft brushing elements be neverthelessfeasible without difficulty.

A third advantage of this device is that it permits a very easy andefficient external protection of the coil assembly by introducing thiscoil for example into a plastic tube 22 of suitable diameter (see FIG.5). This tube may be of commercial type, such as an overchlorinatedP.V.C., having well known properties as far as the resistance to thermaland chemical agents and effects are concerned. In fact, for currentcommercial use this protection is particularly desirable against themechanical actions to which an immersion heater is compulsorily exposedin a manufacturing workshop. However, as in the above-mentioned case ofcable supports, this protection should not involve any interference asfar as the renewal of the fluid to be heated by contact with the cableis concerned, otherwise the cable would be damaged. The presence of theabove-defined rods 5 or hairpins 26 interposed between the inner wall ofthe protection plastic tube and the outer surface of the turns of theheating cable coil will preserve the cable against any detrimentalcontact.

FIG. 1 illustrates a device constituting the outlet of coil 7. The coldoutlets 26, 28 of the cable and the ends 25, 27 of the hairpins or theirequivalents extend through a sealing plug 8 of plastic elastomer or likematerial formed with holes of suitable diameter and secured to the innerwall of a plastic tube 9. The ends of the hairpins may be curved inorder to ensure a safer mechanical anchorage thereof. Only thenon-heating ends of cable 1 emerge therefrom. By properly selecting thedimensions of these elements it is possible, by using a taperedperforated plug 8 and a tapered lower portion of tube 9, to safely wedgethe plug in the tube to seal the assembly at this level. The plug 8 mayconsist for instance of moulded plasticized P.V.C. or like elastomer, orspecial rubber compositions, or halogenated or non-halogenatedpolyolefines. The tube 9 may consist of over-chlorinated P.V.C., orhalogenated or non-halogenated polyolefines.

An adhesive or filling and fastening substance 11 may then be introducedinto the tube for mechanically securing, on setting, the above-describedassembly and provide an additional sealing effect between the cableends, the plastic tube 9 and the bent ends 5 of the longitudinal rods orhairpins 25, 27.

This product 1 1 may consist of a cement capable of resisting to theattack of chemical substances, such as a resin polymerizing in the coldstate by catalysis, with or without the addition of a filler, or a knowncable compound (pitch), or any other filling substance capable ofproviding at the same time the fluid-tightness, protection againstchemical agents and exerting a mechanical assembling action.

The end 30 of plastic tube 9 may be screw-threaded and a plastic hollowelbow 12 may be screwed thereto; alternatively, cemented elbows may beused.

To the other end of elbow 12 another plastic tube 13 may be screwed orcemented in turn, as shown in FIG. 1, for acting both as a support andas a means for fastening the immersion heater to the edge of the vesselcontaining the fluid to be heated, and also for protecting the coldoutlets of the heating cable.

In lieu of this tube 13, a fluid-tight electrical relay (FIG. 4) may besecured to the outlet or rear end of tube 9, between the cold ends 26,28 of heating cable 1 and the conductors of a multiple-conductor cable31, 32, 33. This relay, having a predetermined length, for instance 20cm (8 inch) consists of a plastic tube 14 machined internally to have aslightly tapered wall at either end 15. Plugs 16, 17 of suitableelastomeric material, such as moulded plasticized P.V.C. or specialrubber compositions, are then forced into the ends of tube 14 so thatthe desired sealing effect is obtained by wedging. These plugs areformed with a sufficient number of holes of suitable dimensions for thepassage, through one plug, for example of the two cold outlets 26, 28 ofthe heating cable, and through the other plug, for example of the threeconductors 31, 32, 33 of the outlet cable. After making the electricalconnections,

the tube 14 and perforated plugs 16, 17 are moved to their operativeposition by slipping along it the electrical conductors, and wedged inthe tube ends in order to seal the assembly and provide a reliableinsulation in workshops where the relay is exposed to all kinds ofattacks by the corrosive atmosphere and to splashing with noxiouschemicals. It may be noted that with certain coating of the heatingcable such as halogenated polyolefines any adherence is safelyprecluded, so that also any sealing effect is also avoided except by theresilient tightening of an elastomeric body. The chief advantages ofthis relay are a complete inertia or protection against all theabove-mentioned attacks, in contrast to what is currently observed withmost existing relays. A fluid-tightness providing an absence ofelectrical leakages which is usually obtained by using materialsconsiderably more expensive but without the same properties ofinsensitivity to chemically noxious atmospheres. If desired, thefluid-tightness may be further improved by casting into the tube 14 ofFIG. 4 a suitable commercial product such as pitch, cable compound, aspecial rubber composition, a suitable resin, etc., before closing thetube.

The use of adequately tight relays under frequently severe serviceconditions in electrochemical workshops permits avoiding the use ofheating cables having abnormally long cold outlets which would obviouslybe very expensive, since the cold outlet, by definition, must have thesame insulation as the heating section of the cable. However, it permitstransferring as far as desired away from the working place proper of theimmersion heater any electrical connection to be made in the workshopwhere the heater is actually to be used.

The coil 7, outlet tube and relay 14 (FIG. 5) are covered with asuitable protection tube 22 slipped thereon.

A slit 21 of sufficient length is formed at one end in the protectiontube 22 together with a hole 23 of a diameter corresponding to the outerdiameter of the elbow 12; the protection tube 22 is thus secured verysimply in position by slipping the coil 7 into it. The function of slit21 is to permit the resilient expansion of the protection tube 22 forintroducing the elbow 12 or the tube 13 or alternately the tube 14 intothe hole 23. Slots 24 permitting an easy renewal of the fluid within thetube 22 from the fluid circulating externally in the vessel are alsoformed at spaced intervals along this tube.

An extension of the above-described devices may be used in case it isdesired to supply balanced three-phase current to the immersion heater.In this case three identical cables having suitable electricalproperties are wound simultaneously and in parallel relationship into asingle coil. The three cold outlets thus obtained at the end of the coilmay then be bent to emerge from the opposite end as substitutes for thethree rods 5, and under these conditions, if desired, other hairpins ofcoated wire for the additional rods 5 may be dispensed with. In thedimensional example given hereinabove the perforated plug 8 will thencomprise six holes for the cable ends but no holes for other rods 5. Theperforated plug 16 is also provided with six holes. Thus, inside thetube 14, which may still be merged into the tube 13, the electricalconnection may comprise a balanced three-phase, star-delta circuitleading from the supply network through the multiple-conductor cable.

What I claim is:

1. An immersion heater comprising an insulated heating cable comprisinga major heating portion of resistance wire and opposite end portions ofnon-heating conductive wire, said heating cable being wound into ahelical coil with spaced turns, an insulated support rod bent in hairpinshape with opposite legs connected by a bend, said legs extendinglengthwise of said coil and said bend extending beyond one end of saidcoil, means securing the turns of said coil to said legs, end portionsof said legs and said non-heating end portions of said cable extendingfrom the end of said coil opposite said bend, a plastic tube receivingsaid end portions of said legs and said non-heating end portion of saidcable, setable insulating material embedding said end portions of saidlegs, said non-heating end portions of said cable in said plastic tube3. An immersion heater according to claim 2, comprising relay meansdisposed in said second plastic tube section and connected to saidheater cable, and means sealing said relay means in said second plastictube section.

4. An immersion heater according to claim 1, comprising an electricallyinsulating protection tube fitting over said coil and having spiralslots therein.

1. An immersion heater comprising an insulated heating cable comprisinga major heating portion of resistance wire and opposite end portions ofnon-heating conductive wire, said heating cable being wound into ahelical coil with spaced turns, an insulated support rod bent in hairpinshape with opposite legs connected by a bend, said legs extendinglengthwise of said coil and said bend extending beyond one end of saidcoil, means securing the turns of said coil to said legs, end portionsof said legs and said non-heating end portions of said cable extendingfrom the end of said coil opposite said bend, a plastic tube receivingsaid end portions of said legs and said nonheating end portion of saidcable, setable insulating material embedding said end portions of saidlegs, said non-heating end portions of said cable in said plastic tubeand lead wires connected to said non-heating end portions of said cableto supply electric current thereto, and a plastic stopper closing theend of said plastic tube nearest said coil, said stopper having holestherethrough for said and portions of said legs and said non-heating andportions of said cable.
 2. An immersion heater according to claim 1,comprising a second plastic tube section and a plastic elbow connectingsaid second tube section to said first-mentioned plastic tube.
 3. Animmersion heater according to claim 2, comprising relay means disposedin said second plastic tube section and connected to said heater cable,and means sealing said relay means in said second plastic tube section.4. An immersion heater according to claim 1, comprising an electricallyinsulating protection tube fitting over said coil and having spiralslots therein.